The present invention relates in general to memory controllers and in particular to a method and apparatus for providing concurrent access to a memory by a plurality of data processing devices.
A typical digital oscilloscope includes a digitizer for sampling input waveforms and converting the samples into digital waveform data for storage in a random access waveform memory. Thereafter the waveform data is read out of the waveform memory and transmitted to a display controller which displays the data as a waveform on an oscilloscope screen. Some digital oscilloscopes include microprocessors which may also access the waveform memory for various purposes. For instance a microprocessor may be programmed to read from the waveform memory data sequences representing two waveforms, sum the two sequences to form a third data sequence, and then store the third data sequence in the waveform memory. The third data sequence may be transmitted from the waveform memory to the display controller for display as a "processed" waveform on the screen, the processed waveform representing the sum of the two digitized waveforms.
In such a digital oscilloscope system the digitizer, the display controller, and the microprocessor all access the same waveform memory, and the speed of response of the oscilloscope's display to a change in an input waveform can be limited by the competing demands for access to the waveform memory. What is needed and would be useful is a system for reducing competition for access to a random access memory by a plurality of data processing devices.